docs: def mget(self, pat=None):
          """
          Get a dictionary mapping of all k:v pairs with key matching
          glob style expression `pat`.
          """
          if pat is None:
              return {}
          expr = re.compile(fnmatch.translate(pat))
          m = {}
          for key in tuple(self.keys()):
              #make sure the key is a str first
              if isinstance(key, string_types):
                  if expr.match(key):
                      m[key] = self[key]
          return m